Mesoporous ceria nanoparticles for ultra-fast and highly flexible photo-fenton catalytic reaction

• Crystal structure optimized MCNs can degrade 90% organic dye in 3 minutes. • The MCNs are highly active in wide range of H 2 O 2 concentrations and pH values. • The excellent activity of MCNs is mainly due to the fast adsorption equilibrium rate. Photo-Fenton reactions are quite promising in industrial pollutants degradation by virtue of their high efficiency, low cost and easy operation properties. Ceria is one category of the most versatile inorganic catalysts based on its semiconductor nature and fast Ce 3+ /Ce 4+ exchange capability in the crystal. Recently, ceria has been explored as Photo-Fenton reaction catalysts for pollutants degradation. However, the sharp decrease of catalytic activity in neutral or alkaline solution is in the way of its further practical application. In this study, four mesoporous ceria nanoparticles (MCNs) featured with slight difference of structure parameters were synthesized and their feasibility in catalyzing Photo-Fenton reactions were evaluated. The crystal structure optimized MCNs-240 could realize over 90% dye degradation ratio within 3 minutes, which was much more efficient than the previously reported ceria catalysts. Meanwhile, the change of reaction conditions including the H 2 O 2 concentration (5 to 80 mM) and pH value (2.5 to 8.5) had minimal effects on its catalytic activity. These results implied that the MCNs-240 was an excellent candidate for catalyzing ultra-fast and highly flexible Photo-Fenton reaction. The revealed mechanisms indicated that the fast dye adsorption equilibrium rate and decreased bandgap were the main reasons for the outstanding catalytic performance of the MCNs-240.